Our photo-visual apochromatic Barlow lens is made with real ED glass and offers the correction of the off-axis coma in Newtonian telescopes. This Barlow enables the observation of planets and deep sky objects at the edge of the 1.25" eyepiece field with a quality similar to axis quality. Dobson owners in particular will appreciate this.
The photographically coma-corrected field is designed for the APS-C format (100% illumination at 105mm focus distance). Due to its unique quality, this APO Barlow lens also is usable on telescope systems such as refractors, SC’s and others. An image quality that hardly any other Barlow lens on the market can match, no matter how expensive it is.
The optics, calculated by Gerd Düring from Germany, have been optimized to an aperture ratio of f/4 for systems with a parabolic mirror. This Barlow uses the ED glass FK61 (comparable to Ohara FPL51) as an ED element, it is cemented and equipped with a broadband multicoating on both sides, the transmission is better than 99% in the spectrum from 400nm to 700nm.
The optimal back focus is 105mm from the middle of the last lens. The focal length is - 62.9mm, the free aperture is 22mm.
This coma-correcting Barlow works with a focus distance of 105mm as a perfect optical glass path corrector with integrated coma correction and thus allows the use of normal binocular approaches on telescopes with a short back focus, as is common with Newton / Dobsonian telescopes.
The 2-part adapter is designed photo-visual. Visually with an optimal distance on the APM-Deluxe brass centering clamp. The upper part is 55mm long and can be unscrewed so that a T2 thread (M42 x 0.75mm) appears. Cameras with a total back focus of 55mm (DSLR + T2 ring) can be used easily.
Characteristics:
- Modern optic calculation
- FK61 ED glass
- Visually and photographically usable
- High-quality MC coatings
- Excellent image quality
- Equipped T2 thread
- focus shift outwards 60.65 mm
Delivery:
- APM coma-correcting barlow lens 1.25" 2.7x
- Unscrewable 1.25"barrel
- Protective covers
- Packaging
Products specifications
| Connection to camera | T2 thread |
| Connection to eyepiece | 1 1/4" |
| Housing material | Aluminium |
| Weight | ca. 7 oz |
| Lenses | 2 Lenses |
| Clamping | Brass Clamp |
| Optical design | Cemented Doublet |
| Connection to telescope | 1 1/4" and 2" |
| mechanical path | ca. 120 mm |
| Coating | Broadband Multicoating |
| Unobstructed diameter | 22 mm |
| Magnification | 2.7 x |
| Made for | Newtonian Telescopes (optimized for f/4) |
| Fully illuminated field | minimum 30 mm |
| Resulting focal length | - 62.9 mm |
